Embodiments of the present invention relate to a polishing pad conditioner and methods of manufacturing and recycling.
In the fabrication of the integrated circuits (ICs) and displays, chemical-mechanical planarization (CMP) is used to smoothen the surface topography of a substrate for subsequent etching and deposition processes. A typical CMP apparatus comprises a polishing head that oscillates and presses a substrate against a polishing pad while a slurry of abrasive particles is supplied to polish the substrate. CMP can be used to planarize dielectric layers, deep or shallow trenches filled with polysilicon or silicon oxide, and metal films. It is believed that CMP polishing typically occurs as a result of both chemical and mechanical effects, for example, a chemically altered layer is repeatedly formed at the surface of the material being polished and then polished away. For instance, in metal polishing, a metal oxide layer can be formed and removed repeatedly from the surface of the metal layer during CMP polishing.
However, during the CMP process, the polishing pad collects polishing residue containing ground-off particulate material and slurry by-product. Over time, the polishing residue clogs up the polishing surface of the pad resulting in a glazed polishing pad surface that does not effectively polish the substrate and can even scratch the substrate. For example, in oxide planarization, rapid deterioration in oxide polishing rates with successive substrates results from pad glazing because the polishing surface of the polishing pad becomes smooth and no longer holds slurry between its fibers or grooves, or pores of the pad become clogged with debris. This is a physical phenomenon on the pad surface not necessarily caused by any chemical reactions between the pad and the slurry.
To remedy pad glazing, the pad is periodically conditioned during CMP polishing to restore its original properties by removing polishing residues and re-texturizing the pad surface. A pad conditioner having a conditioning surface with abrasive particles, such as diamond particles, is rubbed against the used polishing surface of the polishing pad to condition the pad surface by removing polishing debris, un-clogging pores on the polishing surface, and forming micro-scratches in the surface of the pad to retain slurry. The pad conditioning process can be carried out either during a polishing process, i.e. known as concurrent conditioning, or after a polishing process.
However, conventional pad conditioners can vary in conditioning ability when the abrasive particles on the pad have physically different structures. For example, when the abrasive particles have different heights, they can cause uneven grooves to be formed on the polishing pad surface. Deeper grooves result in the retention of excessive slurry in the grooves which can cause the substrate portions exposed to those grooves to become excessively eroded. Abrasive particles have been sorted by sizes to reduce these effects, but they are still prevalent in many polishing pad conditioners. Thus it is desirable to have a pad conditioner with a polishing surface that provides uniform and repeatable polishing characteristics even after polishing a number of substrates.
Furthermore, as the pad conditioner is repeatedly used to condition the polishing pad, its effectiveness at reconditioning the polishing surface of the polishing pad gradually decreases because the abrasive particles become worn out and rounded. The abrasive particles of the used conditioner pad can also eventually loosen and fall out. When too many abrasive particles are lost from a region of the conditioning surface, the pad conditioner begins to condition the polishing pad unevenly. The loose abrasive particles can also become embedded in the polishing pad and scratch the substrate during polishing.
Once worn out, the abrasive face of conventional pad conditioners cannot be easily refurbished. The lost abrasive particles cannot be easily replaced with new particles because a relatively strong bond is required between the particles and surrounding matrix, which is difficult to achieve on a used conditioning surface. Thus, in time, when a substantial number of abrasive particles are either worn or lost, the conditioning ability of the pad conditioner so deteriorates that it must be replaced with a new pad conditioner, usually at significant cost. The worn or damaged pad conditioners also result in lower yields from the substrates being polished.
Accordingly, it is desirable to have a pad conditioner that provides more uniform and repeatable polishing characteristics from one polishing pad to another. It is also desirable to have pad conditioners with polishing surfaces that have controllable and reproducible abrasive properties. It is further desirable to be able to recondition the abrasive face of a used pad conditioner. It is also desirable to be able to reuse or recycle pad conditioners, especially when the abrasive particles are expensive or difficult to manufacture.